Synchrotron spectroscopy and torsional structure of the csh-bending and ch3-rocking bands of methyl mercaptan

Lees, Ronald M.

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https://hdl.handle.net/2142/91207 Copy

Description

Title

Synchrotron spectroscopy and torsional structure of the csh-bending and ch3-rocking bands of methyl mercaptan

Author(s)

Lees, Ronald M.

Contributor(s)

• Billinghurst, Brant E.
• Xu, Li-Hong

Issue Date

2016-06-22

Keyword(s)

Spectroscopy of Large Amplitude Motions

Abstract

The Fourier transform spectra of the CSH-bending and CH$_{3}$-rocking infrared bands of CH$_{3}$SH have been investigated at 0.001 cm$^{-1}$ resolution employing synchrotron radiation at the Canadian Light Source in Saskatoon. The relative band strengths and structures are remarkably different from those for the analogous CH$_{3}$OH relative, with the CSH bend being very weak and both the in-plane and out-of-plane CH$_{3}$ rocks being strong with comparable intensities. The CSH bend, centered at 801.5 cm$^{-1}$, has parallel $a$-type character with no detectable $b$-type component. The out-of-plane CH$_{3}$ rock at 957.0 cm$^{-1}$ is a purely $c$-type perpendicular band, whereas the in-plane rock around 1074 cm$^{-1}$ is of mixed $a$/$b$ character. The $K$-reduced $v_{t}$ = 0 sub-state origins for the CSH bend follow the normal oscillatory torsional pattern as a function of $K$ with an amplitude of 0.362 cm$^{-1}$, as compared to 0.653 cm$^{-1}$ for the ground state and 0.801 cm$^{-1}$ for the C-S stretching mode. The torsional energy curves for the out-of-plane rock are also well-behaved but are inverted, with an amplitude of 1.33 cm$^{-1}$. In contrast, the sub-state origins for the in-plane rock do not display a clear oscillatory structure but are scattered over a range of about 2 cm$^{-1}$, with indications of some significant perturbations. The assignments for the three bands all extend up to about $K$ = 10 and are well-determined from GSCD relations, particularly for the $a$/$b$ in-plane rock for which $\Delta$$K$ = 0, +1 and $-$1 transitions are all observed.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

En

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http://hdl.handle.net/2142/91207

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Copyright 2016 by the authors

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